Hereto there exists no device capable of printing a color image directly on a wall surface, etc., of a building, etc., but it is adhered thereon after having once printed on a sheet of paper.
In this case, when a large image is divided into a number of small images, which are printed by means of a color pen device of ink jet system and since ejection of the ink is stopped for every small image, the small images gathered together are lacking in the unity of the tone.
A color enlarging printing device, as indicated in FIG. 11, is developed as a device capable of color-printing a large image at once.
In the figure, A.sub.1 is a printing and recording portion and A.sub.2 is an image inputting and editing portion. The printing and recording portion A.sub.1 consists of a rotating drum G, a motor H, a guide rail I, a micro-spray-gun head J, etc. and the image inputting and editing portion A.sub.2 consists of a camera A, a cylinder for original image B, and oscilloscrope for monitoring C, a control panel D, etc.
In the printing and recording portion A.sub.1 the rotating drum G is supported rotatably by the motor H and the micro-spray-gun head J is disposed movably along the guide rail I in the direction of the length of the drum G.
The spray gun head J is so constructed that compressed air is injected therein so as to eject ink and the amount of ejected ink and therefore the light and shade in the image are adjusted by regulating the flow rate of the air, which is in turn regulated by an actuator.
The main scanning of the printing image is effected by the rotation of the drum G and the auxiliary scanning is effected by the movement of the spray gun head J. The spray gun is displaced from left to right by means of a belt, etc. by utilizing the rotation of the drum G by the motor H.
On the drum G is disposed a rotary encoder and depth signals for each color are read out from a buffer memory in synchronism with signals read out from this encoder. The actuator is driven, responding to these depth signals, so as to control the flow rate of the air injected into the spray gun head J.
On the other hand, in the image inputting and editing portion A.sub.2 the cylinder B is mounted rotatably coaxially to the drum G and when an original image is mounted thereon and it is rotated, scanning of the original image with a narrow light beam begins, starting from a determined point on the original image. Light reflected by the original image changes without interruption due to the rotation thereof. The reflected light, whose intensity varies according to the original image with a high fidelity, is projected into the camera A, where is decomposed into the three primary colors and electric signals corresponding to the respective colors are generated. These electric signals are given to the buffer memory stated above and in this way ink, whose amount varies according to the intensity of these signals, is projected to the sheet of paper mounted on the drum G by the spray gun head J so that a color image is printed in an enlarged scale of the original image.
One of the most serious problematical points of the prior art enlarged image printing device described above is that the enlarged image can be printed only on a sheet of paper, but is not possible to print it directly on a wall surface, etc. of a building.
Further, since it uses a large rotating drum, which should be rotated with a high mechanical precison, and therefore the device for controlling the rotation of the large drum with a high precision is complicated, which makes it very expensive, practical usability thereof is bad and thus it is not widely used.